Cathode for electronic tubes



Jan. 12, 1960 J. E. DRENNAN ETAL CATHODE FOR ELECTRONIC TUBES Filed July 31, 1956 FIG.|

H N ,A N w m N RU W EDLMM O V..0 R m 5 m MMA Q E2 ALR WI- JEF T vv| W 4 y W B United States PatentO 2,921,219 7 CATHODE FOR ELECTRONIC TUBES James E. Drennan and Elmer C. Lusk, Columbus, Ohio, and Francis C. Todd, San Antonio, Tex., assignors to the United States of America as represented by the Secretary of the Army Application July 31, 1956, Serial No. 601,325

2 Claims. (Cl. 313-185) This invention relates to cathodes for use in electron to support the flow of energy therein. Prior to the present invention it was realized that if more than one glow discharge acting in parallel could be incorporated in a tube, a-much larger current capacity forthe tube would result. No satisfactory arrangement however had been found to provide a successful parallel glow operation in a hollow cathode. By supplying additional electrodes of conventional construction in an attempt to establish multiple glow discharge within the cathode, it was found as a practical matter that such parallel operation was not satisfactory. It appeared to be impossible to establish even distribution of the intensity of the discharge throughout the area of the electrodes. Glow discharge activity became concentrated at certain localized areas with a consequent excessive burning and reduction in the life of the cathode.

The present invention provides a structure which makes possible practical operation of two or more glow discharges in parallel within a tube. To achieve this result the cathode is constructed with two outer parallel plates and one or more inner plates received between the outer plates and having a plurality of perforations therein. The perforations provide communication between the discharge regions. Ionized gas travels through the perforations in the inner plate or plates. Thus intense ionization is present on both sides of each center plate. A high intensity glow discharge may thus be created in each discharge region and each discharge operates in parallel during operation of the tube. Moreover, the intensity of discharge is uniformly distributed over the plate surfaces. This arrangement permits greatly increased current fiow through the tube for a given voltage compared to a single glow type of cathode. This increased capacity holds true over a wide range of voltage values. 7

The number of intermediate perforated plates may be increased to obtain increased current capacity. The number of such plates used is limited only by the ability of the tube structure to withstand the high current and to dissipate the heat generated therein.

It is a primary object of the invention to provide a cathode for an electronic discharge device capable of efficiently conducting a relatively high current.

A further object of the invention is to provide a cathode which promotes accurate regulating ability for a tube in which it is used.

A further object of the invention is to provide a cathode having a plurality of glow discharge regions acting in electrical parallelism.

A further object of the invention is to provide a cathode vcc maintains its initial operating characteristics throughout a long life period.

Other objects and features of the invention will more fully appear in connection with the following description and will be particularly pointed out in the claims.

.To provide a better understanding of the invention a particular embodiment thereof will be described and illustrated in the accompanying drawings in which;

Figure 1 is a perspective view illustrating a preferred embodiment of the invention; and

Figure 2 is a cross sectional view on line 22 of Figure 1.

It is to be understood that the principles of the invention have application to electronic discharge devices formany purposes, wherein the hollow cathode construction has usefulness or particular desirability. For purposes of illustration a specific tube type will be described herein in which the cathode of the invention is particularly useful.

=Specific'tube element design, proportions and relative placement has been shown and will be described herein. Suitability for specific applications or load requirements may however dictate particular shapes and proportions differing from those shown.

an anode-'5 shown as a rod of suitable metalha'ving -an The tube illustrated in the drawings is designed to function as a hollow cathode voltage regulating tube having external connection 4 and a cathode 6 composed of three flat parallel plates constructed of metal, such as nickel or molybdenum. Two outer plates 7 embrace an inner plate 8 situated therebetween and parallel to the outer plates 7. The plates are shown as fiat, but may have other conformations and are provided with downwardly directed extensions 9 fastened to supporting devices, such as the wires 10. The wires serve as conductors for connection in a circuit. Each wire is electrically connected to the cathode terminal 11 of the tube. Thus equal voltages are applied to all three of the plates. The anode is connected to its associated circuit in any suitable manner. The plates 7 and 8 have a generally circular outline and form partial annular sections which are situated in a position spaced concentrically from the anode 5 with the plane of the plates perpendicular to the axis of the anode. The particular outline of the anode elements does not constitute a part of the invention. Other designs suitable to a specific application may be used. The tube elements are received within a suitable envelope 12 indicated diagrammatically. The envelope contains an ionizable atmosphere which will be described hereinafter. The spacing of the plates 7 and 8 is adjusted to provide optimum results and to insure consistent operation over along period of usefulness.

The inner plates are perforated by a plurality of apertures 13 whose total area reduces the whole area of the plates by about /5 to /3. The perforations shown are circular, but perforations having other shapes may be used. Desirably also if more than one perforated plate is used, the perforations in adjacent plates should be staggered.

It should be understod that the cathode of the invention may be used in tubes having three or more elements, such as triodes, pentodes and the like.

A suitable atmosphere within the tube envelope has been found to be argon at a pressure of about 20.3 millimeters of mercury. It has also been found that a desirable atmosphere may be created by supplying controlled amounts of a mixture of argon and neon to which a controlled amount of iodine vapor is added. The latter mixture of gases has been found to reduce the amplitude of oscillations within the tube.

Suitable dimensions for the cathode of the type described are as follows: The spacing between the outer for electron discharge devices which is durable and which plates of the cathode and the inner perforated plate is .06

inch. If two or more perforated plates are used their spacings should be between .02 and .06 inch. The diameter of the perforating apertures is .0625 inch. In the tube described the anode to cathode spacing is .500 inch and the anode diameter is .09 inch. The width of the circular portions of the cathode plates is .500 inch. A tube having these dimensions will have a current capacity of the order of 1 ampere. It should be understood however that cathodes of various sizes may be constructed embracing the principles of the invention. When the tube incorporating the cathode is connected in a suitable circuit and supplied with operating voltage, a glow discharge takes place between adjacent plate surfaces and suflicient ionized gas will travel through the perforations in the inner plates to provide intense ionization on each side thereof. Thus a hollow cathode glow is maintained in the region between adjacent plates. These glow discharges function as parallel connected elements in the tube circuit and therefore allow more current to flow.

What is claimed is:

1. In an electronic tube having an envelope containing an ionizable gas sealed therein at low pressure and a rodshaped anode having an external connection, a cathode in said envelope supported in operative relation to said anode comprising a pair of outer metallic, spaced, parallel plates presenting planar continuous surface areas, at least one inner metallic plate between said outer plates and parallel thereto, said inner plate having uniformly distributed perforations therein, said plates of said cathode being perpendicular to said anode, the distance between the said plates being calculated to produce parallel glow discharge between adjacent faces thereof when the tube is supplied with power, and electrical connecting means common to said plates extending outside the tube.

2. In an electronic tube having an envelope containing an ionizable gas sealed therein at low pressure and a rodshaped anode having an external connection, a hollow cathode in said envelope supported in operative relation to said anode comprising a pair of similar outer parallel spaced metallic plates, at least one inner metallic plate between and parallel to said outer plates, said inner plate having substantially the same area as said outer plates and having perforations therein uniformly distributed throughout the area thereof, said plates of said cathode being perpendicular to said anode, and electrical connecting means common to said plates extending outside the said tube, the spacing of said plates being adjusted to produce parallel glow discharges between adjacent faces of the plates when the tube is supplied with power.

References Cited in the file of this patent UNITED STATES PATENTS 1,806,745 De Forest May 26, 1931 1,973,082 Koros Sept. 11, 1934 2,057,522 Henninger Oct. 13, 1936 2,438,356 Alexander Mar. 23, 1948 2,444,072 Stutsman June 29, 1948 2,758,253 Lusk Aug. 7, 1956 

